In connection with an aim of establishing whether there are any function derangements associated with malnutrition this study will determine the short- (7 days) and long- (12 weeks) term effects of oral iron on attention, learning and memory among preschool children. It will be carried out in the Pacific lowlands of rural Guatemala with three groups of preschool children who differ in their body iron status (as indicated by hemoglobin status) as follows: Hgb greater than 11.5 gms.%; (2) 10 less than Hgb less than 11.5; (3) 8 greater than Hgb greater than 10. A secondary purpose is to obtain epidemiological data on zinc nutrition, lead poisoning and morbidity among the same sample of children. A first screening of the hematological conditions of 98 children between 3 and 6 years of age where the study will be conducted has been already completed. Prevalence data indicate a high number of both moderate and severe cases of sideropenia. A behavioral pilot study in villages near where the study will be conducted has also been completed to determine the cultural fitness of the psychological tools to be used. Research will use a prospective before- and after-treatment design (including placebo) with six subgroups of children of equal size matched on sex, age, anthropometry and SES. Assignment of the two subgroups within each of the three hematologic conditions will be randomized. Behavioral data will be collected before initiation of treatment, after short- and long-term treatment. Intra-individual and interindividual comparisons will therefore be made in data analysis. Data collection includes clinical and anthropometric measurements; biochemical and hematologic determinations; and behavioral evaluations. Behavioral tests are selected from a theory that differentiates structural from process features of cognition.